. I

NASA Technical Memorandum 88942 ,

PMR Polyimide Compositions for Improved Performance at 371 "C

{NASA-TPl-88942) EnR F C L Y I M I G E C O X P O S I T I O N S N e 7- 16C 71 EOR I H P E O V E D F E E F S K H A N C E A 1 371 BEG C [ N A S A ) 1 3 p CSCL 11D

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Unclas 63/24 4 3 3 6 9

Raymond D. Vannucci Lewis Research Center Cleveland, Ohio

Prepared for the 32nd International SAMPE Symposium and Exhibition Anaheim, California, April 6-9, 1987

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https://ntrs.nasa.gov/search.jsp?R=19870006638 2019-12-31T00:50:48+00:00Z

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PMR POLYIMIDE COMPOSITIONS FOR IMPROVED PERFORMANCE AT 371 O C

Raymond 0. Vannuccl National Aeronautics and Space Admin is t ra t ion

Lewis Research Center Cleveland, Ohio 44135

SUMMARY

Studies were conducted t o i d e n t i f y ma t r i x res ins which have p o t e n t i a l f o r use a t 371 "C (700 O F ) . U t i l i z i n g PMR methodology, neat r e s i n moldings were prepared w i th various monomer reactants and screened f o r thermo-oxidative sta- b i l i t y a t 371 O C (700 OF) under both ambient and fou r atmospheres a i r pressure. The r e s u l t s o f the r e s i n screening studies i nd i ca te t h a t h igh molecular weight (HMIJ) formulated res ins o f f i r s t (PMR-15) ( r e f . 1) and second (PMR-11) ( r e f . 2) generation PMR mater ia ls e x h i b i t lower l eve l s o f weight loss a t 371 O C (700 O F )

than PMR-15 and PMR-I1 res ins. The resin systems which exh ib i t ed the best o v e r a l l balance o f p rocessab i l i t y , Tg and thermo-oxidative s t a b i l i t y a t 371 'C were used t o prepare un id i rec t i ona l Celion 6000 and T-40R graph i te f i b e r laml- nates. Laminates were evaluated f o r thermo-oxidative s t a b i l i t y and 371 O C

mechanical proper t ies. Results o f the laminate eva lua t ion s tud ies Ind i ca te t h a t two o f t he r e s i n compositions have p o t e n t i a l f o r use i n 371 O C appl ica- t i ons . The most promising r e s i n compositlon provided laminates which exh ib i t ed no drop i n 371 O C mechanical proper t ies and only 11 percent weight loss a f t e r 200 h r exposure t o 4 atmospheres o f a i r a t 371 O C .

INTRODUCTION

The ob jec t i ve o f the polymers research being conducted a t NASA Lewis Research Center i s t o develop technology f o r new generations o f organic po ly- mers intended f o r app l i ca t i on i n advanced aeropropulsion systems. Studies t o improve a i r c r a f t engine performance have ind ica ted t h a t advanced designs w i l l d i c t a t e h igher thrust-to-weight r a t i o s than present day l eve l s . achieved through the use o f advanced l lgh twe igh t composite mater ia ls . the requirements fo r h igh temperature advanced composites, NASA Lewis developed the PMR polyimides ( r e f . 1). Today PMR polyimides are t h e leading ma t r i x res ins f o r h igh temperature advanced polymer mat r ix composites and are commer- c i a l l y ava i l ab le from a number o f suppliers. The technology f o r app l i ca t i on o f these advanced composite mater ia ls i s developing rap id l y . A t the present time, PHR mater ia ls a re being used i n a number o f composite engine components c u r r e n t l y i n production or soon t o be introduced i n t o production. While cur- r e n t engine app l ica t ions o f PMR mater ia ls have resu l ted i n some s i g n i f i c a n t cos t and weight savings, t h e i r app l i ca t ion has been l i m i t e d t o engine sections operat ing i n the 200 t o 300 O C (392 t o 572 O F ) temperature range. Further b e n e f i t s can be rea l i zed by moving composites I n t o t h e higher temperature regions on engines.

This can be To meet

The purpose o f t h i s study was t o i nves t i ga te higher molecular weight (HMW) PMR r e s i n formulations and t o determine the e f f e c t o f these formulat ions on r e s i n and composite physical propert ies, thermo-oxidative s t a b i l i t y , and mechanical p roper t ies a f t e r exposure I n a i r a t 371 O C (700 O F ) .

J

EXPERIMENTAL PROCEDURE

Resin Preparat ion

The'monomer reactants used t o prepare the res ins inves t iga ted i n t h i s study are shown i n t a b l e I . A l l o f the monomers except the dimethylesters were purchased from commercial suppl iers . The dimethylesters (BTDE and HFDE) were prepared as 50 w t % methanol so lu t ions by r e f l u x i n g a suspension of the cor- responding dianhydride I n anhydrous methanol u n t i l a l l so l i ds had dissolved and then f o r an add i t iona l 2 hr.

PMR reactant so lut ions were prepared a t room temperature by d i sso l v ing the reactants i n anhydrous methanol t o form 30 t o 50 w t % so l i ds so lut ions. The s to ich iomet r ic r a t i o o f the monomers used f o r t he a d d i t i o n cur ing res ins pre- pared was as fo l lows: n moles o f d imethylester, n t 1 moles o f diamine, and 2 moles o f NE.

Neat r e s i n moldings were prepared by p lac ing so lu t ions conta in ing 1 5 g o f so l i ds I n t o an a i r c i r c u l a t i n g oven set a t 121 *C (250 O F ) u n t i l a l l o f the so lvent had evaporated and the reactants were p a r t i a l l y imidized. The dry mater ia l was then crushed and the oven temperature increased t o 177 t o 204 O C

(350 t o 400 O F ) , depending on r e s i n formulated molecular weight (FMW), f o r 1 hr t o complete the im id i za t i on t o the endcapped prepolymer. The Imidlzed mate- r i a l was then ground i n t o a f i n e powder. placed I n t o a 2-in. diameter metal d i e a t room temperature. The d i e ( w i t h thermocouples attached) was placed I n t o a press preheated t o 316 t o 343 O C

(600 t o 650 OF). When the temperature o f the d i e reached 260 O C (500 O F ) , a pressure ranging between 6.9 t o 13.8 MPa (1000 t o 2000 p s i ) was appl ied. ' F i n a l cure temperature and pressure was dependent on the FMW o f the res in . Higher FWls required higher cure temperatures and pressures. F ina l cure temperature and pressure was maintained f o r 2 h r . A f te r cur ing, the moldings were al lowed t o cool under pressure t o 232 O C . A t 121 O C (250 O F ) the moldings were removed from the d i e and postcured i n an a i r c i r c u l a t i n g oven programed t o heat a t 6 OC/min t o 260 O C and then 1 O C t o 371 O C , fo l lowed by a 24-hr ho ld a t 371 O C .

Approximately 4 g o f powder was then

Laminate Fabr ica t ion

A l l laminates were prepared from u n i d i r e c t i o n a l g raph i te re in fo rced pre- preg tape. The reinforcements used i n t h i s study included Cel ion 6000 and Amoco's T-40R graphi te f i b e r . o f r e s i n solut ions onto drum wound un id i rec t i ona l f l b e r ca lcu lated t o y i e l d laminates having 58 vo l x f i b e r a f t e r cur ing. The prepreg was allowed t o d ry on the drum under quar tz lamps t o a v o l a t i l e content o f 11 t o 12 w t %. The prepreg was then removed from the drum and cu t I n t o 7.62- by 20.3-cm (3- by 8-111.) p l i es and a number o f p l i e s stacked u n i d i r e c t i o n a l l y i n t o a pre- form staging too l t o y i e l d laminates having a cured thickness o f 0.20 t o 0.23 cm (0.080 t o 0.090 i n . ) . The prepreg stacks were then heated under 0.1 p s i of pressure f o r 60 min a t temperatures o f 177 t o 204 O C (350 t o 400 O F ) . Laminates were then compression molded by p lac ing the staged layup i n t o a f l a t matched metal d i e a t room temperature and then i n s e r t i n g the d i e i n t o a press preheated t o e i t h e r 316 O C (600 O F ) o r 343 O C (650 O F ) . When the d i e reached 232 O C (450 O F ) a pressure ranging from 3.45 t o 17.3 MPa (500 t o 2500 p s i ) was applied. When the d i e reached the f i n a l cure temperature, pres-

Prepreg tapes were prepared by brush app l i ca t i on

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sure and temperature were maintained for 2 hr. to cool slowly to 23-2 O C (450 OF) (-45 min) under pressure and then fast cooled without pressure to room temperature. cured according to the same postcure schedule used for neat resin moldings.

The laminates were then allowed

All laminates were then post-

371 "C Isothermal Aging

Isothermal welght loss measurements were performed on neat resin and lami- nates after exposure to air at 371 O C under both 1 and 4 atm of pressure. A forced-air oven was used for 1 atm exposure and the air change rate employed was 100 cc/min. per hour In a 2.0 liter autoclave chamber.

The air change rate for 4 atm exposures was five air changes

LAMINATE EVALUATION

Prior to testing all laminates were inspected for porosity using an ultra- sonic C-Scan technique.

Flexural and Interlaminar Shear Tests

Flexural strength and interlaminar shear strength (ILSS) tests were

Flexural strength tests were performed on 0.635- by 7.62-cm performed on specimens ranging in thickness from 0.20 to 0.23 cm (0.080 to 0.090 in.). (0.25- by 3.0-in.) specimens in accordance with ASTM D-790 at a constant span/ depth of 28. in accordance with ASTM D-2344 at a span/depth of 5. Elevated temperature tests were performed in an environmental heating chamber. Property values reported are averages of three to six tests.

ILSS tests were performed on 0.635 cm (0.25 in.) wide specimens

RESULTS AND DISCUSSION

Resin Screening Studies

Table I lists the monomer reactants used to prepare the resins investi- gated. Table I1 identifies the composition of each of the resins. All of the resins contained NE. The stoichiometric ratio of the reactants used for each of the resins was i n the ratio n/(n + 1)/2, where n = moles of dimethylester, n + 1 = moles of diamine and 2 = moles of NE. The value of n ranged between 1.67 and 14.5. The formulated molecular weights (FMW) ranged between 1270 and 7500 for the end-capped prepolymers prior to final curing of the resin. number included in the resin designation corresponds to the FMW of the resin, i.e., 15 = 1500, 30 = 3000. Two of the formulatlons contained a mixture of diamines and were desjgnated MD. of NE presented in each of the resin formulations.

The

Also shown in table I1 is the weight percent

Table I11 lists the percent weight loss for each of the neat resins after exposure to air at 371 O C under both 1 atm and 4 atm of pressure. are the resin glass transition temperatures (Tg's) after 24 hr and 50 hr exposure to air at 371 O C and 1 atrn o f pressure.

Also shown

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The 4 atm, 371 O C exposure cond i t ion was selected t o s imulate the condi- t i o n whichecomposites would experience I n an engine zone operat ing a t 371 O C .

The t a b l e shows t h a t the 371 O C ox ida t i ve s t a b i l i t y of both PMR and PMR-I1 r e s i n formulations improve as the FMW i s increased. This i s a r e s u l t o f t he reduct ion i n a lphat ic content due t o the Nadic endcap w i t h increas ing FW as shown i n t a b l e 11. However, the data shows t h a t PMR r e s i n FMU's higher than 5000 o f f e r no fu r ther improvements i n 371 O C ox ida t i ve s t a b i l i t y . probably due t o d i f f i c u l t y i n processing res ins having h igh FMW's. It can be seen t h a t t he MR-I1 res ins e x h i b i t considerably b e t t e r thermo-oxidative resistance (TOS) than the other formulat ions invest igated. This i s due t o the more thermal ly stable reactants (HFDE, PPDA) used i n the PMR-I1 res ins. Note t h a t PMR-11-13 having the highest NE content (25.2 w t X), exh ib i ted compara- b l e weight loss , under both exposure condi t ions, t o t h a t o f the hlgher FMW PMR and MD res ins which contained considerably lower NE content. exh ib i ted by the PMR-11-50 r e s i n was achieved i n s p i t e o f the presence o f b l i s t e r s which developed dur ing the 24-hr 371 O C postcure p r i o r t o the aging study. low Tg exhib i ted by the HMW PMR-11-30 res in .

This i s

The exce l len t TOS

B l i s t e r i n g might be due t o the presence o f unreacted mater ia l and the

Cornparing the Tg's o f res ins a f t e r 50 hr exposure under 1 atm shows t h a t the res ins containing BTDE and a mixture o f the diamines BDAF and PPDA (HD-60 and MD-64), exh ib i t s i g n i f i c a n t l y higher Tg's than the other formulat ions. While the NE content o f these HMW formulat ions i s -5 w t 96, there appears t o be a h igh degree o f ox ida t ive c ross- l ink ing tak ing place as a r e s u l t o f the carbonyl and ether l inkages present I n BTDE and BDAF, respect ive ly .

Laminate Studies

The res ins selected f o r laminate studies included a l l the res ins l i s t e d i n tab le I1 except MD-64 and PMR-11-50. laminates was un id i rec t iona l Cel ion 6000 graph i te f i b e r .

The reinforcement used t o prepare the

Figure 1 compares the weight loss o f the laminates as a func t i on o f exposure ttme i n a i r a t 371 O C and 4 atm o f pressure. as expected, the PMR-11-30 laminate exh ib i ted the lowest 200 h r weight loss (12.5 w t 96) whi le the PHR-15 laminate exh ib i ted the h ighest weight loss (24 ut X) a f t e r only 120 h r o f exposure. Laminates prepared from a l l other res ins exhib i ted comparable weight loss (23 t o 24 w t X ) a f t e r 200 h r exposure.

The f i g u r e shows tha t , '

Figure 2 compares the re ten t i on o f in te r laminar shear s t rength (ILSS) o f the laminates a f t e r exposure t o 4 atm o f a i r a t 371 "C. The f i g u r e shows t h a t the laminates prepared from PMR-15 and MD-60 res in , which exh ib i ted the high- es t r e s i n Tg's, a lso exh ib i ted the highest i n i t i a l ILSS when tes ted a t 371 O C .

The HD-60 laminate reta ined 65 percent o f i t s i n i t i a l ILSS a f t e r 200 hr expo- sure, wh i le the PHR-15 laminate reta ined only 50 percent o f i t s i n i t i a l 371 O C

ILSS a f t e r on ly 120 h r o f exposure. The laminates prepared from PMR-11-18 and PMR-11-80 exhibi ted the lowest i n i t i a l 371 O C ILSS, bu t e s s e n t i a l l y re ta ined t h a t s t rength throughout the exposure time.

Figure 3 compares the re ten t i on o f 371 O C f l e x u r a l s t rength f o r the same laminates exposed under the same condi t ions discussed above. The f i g u r e shows

4

that the 371 OC flexural strength retention of the laminates are In c?ose agreement with the results shown for 371 OC ILSS retention.

Based on the results of studies shown so far, It can be concluded that the PMR-11-30 resin offers the highest potential for use as a matrix resin for 371 OC composite applications. It must be noted that while the laminates pre- pared from the MD-60 resin exhibited nearly twice the weight loss shown for the PMR-11-30 laminates during exposure to 371 OC air, the laminates prepared from MD-60 resin exhibited the highest mechanical properties over very nearly the entire 371 OC exposure time. However, MD-60 laminates as well as the laminates prepared from PMR-15, 30, 50 resins exhibited a significant amount of loose surface fiber after 100 hr exposure to 371 OC air at 4 atm, while the PMR-11-30 laminate exhibited no loose surface after 200 hr of exposure. determine any possible effect o f the reinforcing fiber on the oxidative weight loss of the laminates, additional laminates were fabricated using Amoco's T-40R graphite fiber which exhibits significantly better oxidative stability during exposure to air at 371 "C and 4 atm pressure than Celion 6000 graphite fiber.

In order to

Figure 4 compares the weight loss of laminates prepared from MD-60 and PMR-11-80 resins with both Celion 6000 and T-40R fiber reinforcements during exposure to air at 371 OC and 4 atm of pressure. Also shown are the weight losses of Celion 6000 and T-40R bare fiber exposed to the same conditions for 120 hr. The figure shows that after 200 hr of exposure, the T-40R/MD-60 lami- nate exhibited 5 percent less weight loss than the Celion 6000/MD-60 laminate. The T-40R/PMR-II-30 laminate exhibited 3 percent less weight loss than the Celion 6000/PMR-II-30 laminate after 200 hr of exposure. The T-40R/MD-60 lami- nate still exhibited loose surface fiber after 100 hr exposure, but to a lesser degree.

Figure 5 compares the 371 O C flexural strength retention of the laminates compared in figure 4 as a function of exposure time in 371 OC air at 4 atm. It can be seen that the flexural properties of the T-QOR/MD-60 were slightly lower than those of the Celion 6000/MD-60 laminate over the entire exposure time. No appreciable differences are apparent for the flexural strength reten- tions shown for the two laminates prepared from the PMR-11-30 resin. Note that, again, at the end of 200 hr exposure, the MD-60 system seems to be losing strength rapidly, while the PMR-11-30 system curve remains flat.

Based on the results of this study, the following conclusions can be drawn :

1. A PMR-I1 resin composition has been identified (PMR-11-30) which has potential for use in engine zones operating at temperatures up to 371 "C.

2. The use of higher FMW PMR compositions results in enhanced oxidative stability during exposure to air at 371 OC.

3. Higher FMW PMR compositions require higher cure pressures to yield high quality laminates.

REFERENCES

1. Serafini, T.T., Delvigs, P., and Llghtsey, G.R.: Thermally Stable Polyimides from Solutions o f Monomeric Reactants, Journal of Applied Polymer Science, Vol. 16, No. 4, Apr. 1972, pp. 905-915.

2. S e r a f i n l , T.T. Vannuccl , R.D. and 4 1 s t o n v W.B.: Second Generatlon PMR Polylmides, NASA TU X-71894, 1976.

6

TABLEI. - MONOMERS USED FOR FOLYlMlDE SYNTHESIS

STRUCTURE NAME ABBREVIATION

0 It

0 0 0

H3CO -CJ@J!~C II II - OCH3

C -OH II

HO -C II 0 0

0 0

MONOMETHYL ESTER OF 5-NORBORNENE-2,3- DICARBOXYLIC ACID

DIMETHYL ESTER OF 3,3'4,4'- BENZOPHENONETETRACARB OXYLlC ACID

DIMETHYL ESTER OF 4,4'- (HEXAFLUOROISOFR0PYLIDENE)- BIS(PHTHAL1C ACID)

4,4'-METHYLENEDIANI LINE

P-PHENYLENEDIAMINE

B IS (AM IN OPHEN OX Y 1 PHENYLHEXAFLUOROPROPANE

NE

BTDE

HFDE

MDA

PPDA

BDAF

TABLE 11. - COMPOSITIONS OF RESINS INVESTIGATEDa

388 375 375 370 398 403 381 368 355

Res i n

PHR-15 ( c o n t r o l ) PMR-30 PMR-50 PMR-75 HD-64

MD-60

PHR- 11-1 3 PMR-11-30 PMR- 11-50

300 h r / l atm 75 h r / 4 atm

18.0 18.2 12.0 14.0 13.0 13.0 16.5 13.8 16.0 17.0 12.2 14.0 13.0 12.3

8.0 6.4 5.5 5.0

~ D i e s t e r I Diamine

PMR-15 ( c o n t r o l ) PHR-30 PHR-50 PHR-75 HD-64 HD-60 PMR-11-13 PHR-11-80 PHR- I I - 50

BTDE BTDE BTDE BTDE BTDE

BTDE

HFDE HFDE HFOE

370 365 363 358 370 370 368 345 340

BDAF/PPOA 3:2

BDAF/PPDA 1 :1

PPOA PPDA PPDA

ut % NE

21.8 10.9

6.5 4.4 5.1

5.4

25.2 10.9

6.5 I I I I I I

aResin s t o i c h i o m e t r y : NE/Diester/Diamine Holes: 2/ n /n t 1

TABLE 111. - R E S I N WEIGHT LOSS DURING EXPOSURE TO ONE AND FOUR

ATMOSPHERES OF A I R AT 371 O C

Res i n Tg "Ca Tg "Cbl Percent we igh t l o s s a f t e r : I

0

5 k

k! 10

W V CL

. v) v) 0

I- S (3

W

W c

c, 15

Y

= 20

9 U 3 25

30

0 \

\ s3

O PMR-30

8 Z7 * 0 PMR- 11-13

PMR- 11-30

\ 0 '@

0 50 100 150 200 TIHE, HR

Figure 1 .-Weight loss of Cel ion 6000 graphite/PMR laminates exposed in 4 atm. o f air at 371OC.

KS I 0 -

60

50

40

20

RESIN - 0 PUR-15

-

-

-

-

c W z W oc c v)

PI U W I v)

PI U z z U A QI W t- z

Y

Y

1oool-

800 I l- a z 2 600- 2 a 4 e % W

LL

= 400-

200-

-

M Pa

U

O PMR-30

7

6

5

4

3 TESTED AT 3710C

O PMR-30 A PMR- 50

-

3 1 TESTED AT 3710C

0 50 100 150 200 TIME, HR

F igure 2.- I n te r l am ina r shear s t reng th o f Cel ion 6000 graphite/PMR laminates a f t e r exposure t o 4 atm. o f a i r a t 371OC

- RESIN O PMR-15 0 PMR-JO

PnR- 50 HD- 60 PMR- 11-13

tS PMR-11-30

KS I 140 -

100

80

TESTED AT 371OC 60 - 0

KS I 140 I;

d PMR- 11-13 tS PMR-11-30

120

100

80

60 U

1 I I 1 50 100 150 200

TIME, HR

F igure 3.-Flexural s t reng th o f Ce l ion 6000 gra- phite/PMR l p i n a t e s a f t e r exposure t o 4 atm. o f a i r a t 371°

O2iGELVAP PAGE IS OF POOR QUALITY

1000

I

z w p: c v)

800

2 600 3 => % w

400

200

FIBER/RES I N 1-40R FI"'"

n

-

-

-

-

Cel ion 6000/MD-60

$3 Cel ion 6000/PHR-11 "r . . s b DLnl a 8 T-4OR/MD-60

8 T-4OR/PMR- 11-30

I W I Y 0 50 100 150 200

Figure 4.-Weight loss of laminates prepared from Celion 6000 graphite a n d T-40R graphite fibers, after exposure t o 4 atm. of a i r a t 371OC

TIME, HR

MPa

-30

FIBER/RESIN

Cel Ion 6000/MD-60 KS I 8 T-40R/MD-60

13Celion 6000/PHR-I1-30 8 T-40R/PMR- 11-30 \

120 1 ------l

80

"1 TESTED AT 371%

I I I I 50 100 150 200

40 I 0

Figure 5 .-Comparison o f flexural strength reten- t i o n of laminates prepared from Celion 6000 and T-40R graphite fiber af ter exposure t o 4 atm. of a i r a t 3710C

TIME, HR

1. Report No.

NASA TH-88942 4. Title and Subtltle

12. Government Accession No.

5. Report Date

1 3. Reclplent's Catalog No.

PHR Polyimlde Compositions f o r Improved Performance a t 371 O C

7. Author@)

6. Performing Organization Code

505-53-01 8. Performlng Organlzatlon Report No.

9. Performlng Organlzatlon Name and Address

National Aeronautics and Space Admin is t ra t ion Lewis Research Center Cleveland, Ohio 44135

2. Sponsorlng Agency Name and Address

National Aeronautlcs and Space Admin is t ra t ion Washington, D.C. 20546

Raymond D. Vannucci

11. Contract or Grant No.

13. Type of Report and Perlod Corered

Technical Memorandum 14. Sponeoring Agency Code

I E-3390

7. Key Words (Suggested by Authofls))

10. Work Unlt No.

18. Dlstrlbutlon Statement

9. Security Classlf. (of this report)

Unc lass i f ied

5. Supplementary Notes

20. Securlty Classlf. (of this page) 21. No. of pages 22. Prlce'

Unclass i f ied

Prepared f o r the 32nd In te rna t i ona l SAHPE Symposium and Exh ib i t ion , Anaheim, Ca l i f o rn ia , A p r i l 6-9, 1987.

6. Abstract

Studies were conducted t o i d e n t i f y ma t r i x res ins which have p o t e n t i a l f o r use a t 371 O C (700 O F ) . U t i l i z i n g PHR methodology, neat r e s i n moldings were prepared w i t h various monomer reactants and screened f o r thermo-oxidative s t a b i l i t y a t 371 O C (700 O F ) under both ambient and four atmospheres a i r pressure. resu l t s o f the res in screening studies i nd i ca te t h a t h igh molecular weight (HMJ) formulated res ins of f i r s t (PHR-15 ( r e f . 1)) and second (PHR-I1 ( r e f . 2)) gener- a t i o n PHR mater ia ls e x h i b i t lower l eve l s o f weight loss a t 371 O C (700 O F ) than PHR-15 and PHR-I1 resins. balance o f processabi l i ty , Tg and thermo-oxidative s t a b i l i t y a t 371 O C were used t o prepare un id i rec t iona l Cel ion 6000 and T-40R graph i te f i b e r laminates. Lami- nates were evaluated f o r thermo-oxidative s t a b i l i t y and 371 O C mechanical proper- t i e s . Results o f the laminate evaluat ion studies i nd i ca te t h a t two o f the r e s i n compositions have po ten t i a l f o r use i n 371 O C appl icat ions. The most promising r e s i n composition provided laminates which exh ib i ted no drop i n 371 O C mechanical proper t ies and only 11 percent weight loss a f t e r 200 h r exposure t o 4 atmospheres o f a i r a t 371 O C .

The

The r e s i n systems which exh ib i ted the best o v e r a l l

Polymide res in ; Composites; High temperature resins; Polymer matr ix res ins

Unc lass i f ied - un l im i ted STAR Category 24